Substrate table assembly, an immersion lithographic apparatus and a device manufacturing method

1. A substrate table assembly for an immersion lithography apparatus, the substrate table assembly comprising: a substrate table to support a substrate; and a gas handling system to provide a gas to a region between the substrate table and a substrate mounted on the substrate table, wherein the gas provided by the gas handling system has a thermal conductivity greater than or equal to 100 mW/(m·K) at 298 K, wherein the substrate table comprises a supply port to supply the gas from the gas handling system to the region between the substrate and the substrate table, and an extraction port to extract fluid from the region, the extraction port comprising a peripheral extraction port configured to provide a laterally inward flow of ambient gas, immersion fluid, or both, from a region adjacent to the periphery of the substrate and configured to extract at least some of the gas at a same time as providing the inward flow, wherein the substrate table is configured to provide an open flowpath underneath the substrate when provided on the substrate table, that connects the supply port and the peripheral extraction port and configured to allow the gas from the supply port to cover a majority of the bottom surface of the substrate when provided on the substrate table.

2. The substrate table assembly according to claim 1 , wherein the supply and extraction ports are configured to provide a laterally outward flow of the gas provided by the gas handling system in a region directly adjacent to the peripheral extraction port.

3. The substrate table assembly according to claim 2 , further comprising a peripheral flow restricting structure in the form of a closed path to restrict flow of fluid between a laterally inner and a laterally outer portion of the region between the substrate and the substrate table, relative to a center of the substrate and/or substrate table.

4. The substrate table assembly according to claim 3 , wherein the peripheral flow restricting structure comprises an inner peripheral flow restricting structure and an outer peripheral flow restricting structure, the inner peripheral flow restricting structure being surrounded by the outer peripheral flow restricting structure.

5. The substrate table assembly according to claim 4 , wherein the peripheral extraction port is located between the inner and outer peripheral flow restricting structures.

6. The substrate table assembly according to claim 5 , further comprising an intermediate peripheral flow restricting structure between the inner and outer peripheral flow restricting structures.

7. The substrate table assembly according to claim 6 , wherein the peripheral extraction port is located within at least two of the regions between adjacent peripheral flow restricting structures.

8. The substrate table assembly according to claim 1 , further comprising a buffer gas supply port configured to supply buffer gas to the region between the substrate table and a substrate mounted on the substrate table.

9. The substrate table assembly according to claim 1 , wherein the gas handling system comprises a continuous flow system to provide a continuous flow of the gas having a thermal conductivity greater than or equal to 100 mW/(m·K) at 298 K at a substantially constant pressure, the pressure being lower than atmospheric pressure.

10. A substrate table assembly for an immersion lithography apparatus, the substrate table assembly comprising: a substrate table to support a substrate; and a gas handling system to provide a gas to a region between the substrate table and a substrate mounted on the substrate table, wherein the gas provided by the gas handling system has a thermal conductivity greater than or equal to 100 mW/(m·K) at 298 K, wherein the substrate table comprises a supply port to supply the gas from the gas handling system to the region between the substrate and the substrate table, and an extraction port to extract fluid from the region, the extraction port comprising a peripheral extraction port configured to provide a laterally inward flow of ambient gas, immersion fluid, or both, from a region adjacent to the periphery of the substrate and configured to extract at least some of the gas at a same time as providing the inward flow, wherein the substrate table is configured to provide an open flowpath underneath the substrate when provided on the substrate table, that connects the supply port and the peripheral extraction port and configured to allow the gas from the supply port to cover a majority of the bottom surface of the substrate when provided on the substrate table, and wherein the substrate table comprises a through-hole having an opening into the region between the substrate and the substrate table.

11. The substrate table assembly according to claim 10 , further comprising a through-hole flow restricting structure surrounding the opening of the through-hole.

12. The substrate table assembly according to claim 10 , further comprising a through-hole extraction port to extract fluid from the region adjacent to the opening of the through-hole.

13. The substrate table assembly according to claim 12 , wherein the through-hole flow restricting structure comprises an inner through-hole flow restricting structure and an outer through-hole flow restricting structure, both surrounding the opening of the through-hole, the through-hole extraction port being located between the inner and outer through-hole flow restricting structures.

14. The substrate table assembly according to claim 13 , further comprising an intermediate through-hole flow restricting structure between the inner and outer through-hole flow restricting structures.

15. The substrate table assembly according to claim 14 , wherein the through-hole extraction port is located within at least two of the regions between adjacent though-hole flow restricting structures.

16. The substrate table assembly according to claim 10 , further configured to supply a flow of buffer gas towards the substrate through the through-hole.

17. The substrate table assembly according to claim 10 , wherein the substrate table comprises a through-hole supply port to supply the gas having a thermal conductivity greater than or equal to 100 mW/(m·K) at 298 K to the through-hole such that in at least a portion of the through-hole a gas flow away from the substrate is established.

18. The substrate table assembly according to claim 10 , wherein the through-hole is configured to provide access to a pin for use during mounting or unmounting of the substrate from the substrate table or to a pin for alignment of the substrate table relative to a mounting block for the substrate table.

19. A device manufacturing method, comprising: projecting a patterned beam of radiation through an immersion liquid confined to a space between a projection system and a substrate; providing gas to a region between the substrate and a substrate table using a supply port, wherein the gas has a thermal conductivity greater than or equal to 100 mW/(m·K) at 298 K; providing a laterally inward flow of ambient gas, immersion liquid, or both, from a region adjacent to the periphery of the substrate using a peripheral extraction port; and extracting at least some of the gas using the peripheral extraction port at a same time as providing the inward flow, wherein there is an open flowpath underneath the substrate that connects the supply port and the peripheral extraction port and wherein the gas from the supply port covers a majority of the bottom surface of the substrate.

20. A device manufacturing method, comprising: projecting a patterned beam of radiation through an immersion liquid confined to a space between a projection system and a substrate; providing gas to a region between the substrate and a substrate table using a supply port, wherein the gas has a thermal conductivity greater than or equal to 100 mW/(m·K) at 298 K; providing a laterally inward flow of ambient gas, immersion liquid, or both, from a region adjacent to the periphery of the substrate using a peripheral extraction port; and extracting at least some of the gas using the peripheral extraction port at a same time as providing the inward flow, wherein there is an open flowpath underneath the substrate that connects the supply port and the peripheral extraction port and wherein the gas from the supply port covers a majority of the bottom surface of the substrate, wherein the substrate table comprises a through-hole having an opening into the region between the substrate and the substrate table.